Oral care compositions comprising pearlescent pigments

ABSTRACT

The invention provides an oral care composition suitable for delivering a temporary whitening effect to the surface of teeth, the composition comprising: a continuous phase comprising water or polyhydric alcohol or a mixture thereof; a tooth surface whitening agent which is dispersed in the continuous phase, and a deposition aid for the tooth surface whitening agent; characterized in that the tooth surface whitening agent is a pearlescent pigment in an amount of at least 0.1% by weight based on the total weight of the composition, the pearlescent pigment being formed by coating one or more metal oxide layers onto particles of an inorganic substrate.

FIELD OF THE INVENTION

The present invention is concerned with oral care compositions. Moreparticularly, the present invention is concerned with oral carecompositions containing pearlescent pigments.

BACKGROUND OF THE INVENTION

The colour of the teeth is influenced by a combination of theirintrinsic colour and the presence of any extrinsic stains that may formon the tooth surface. Extrinsic colour is linked with the adsorption ofmaterials into the acquired pellicle on the surface of enamel, whichultimately cause staining. Factors that influence extrinsic stainformation include poor tooth brushing technique, smoking, dietary intakeof coloured foods (e.g. red wine), subject age and the use of certaincationic agents such as chlorhexidine or metal salts like tin and iron.

Consumers have always had a strong desire for white teeth and manyindividuals are dissatisfied with their current tooth colour. Thisdesire for whiter teeth has given rise to a growing trend in theincreased use of tooth whitening products.

Current whitening toothpastes rely on optimised abrasive and chemicalcomponents to maximise stain removal and prevention. During brushing,abrasive particles become temporarily trapped between the toothbrush andthe stained tooth surface and abrade away the stain. Chemical componentsmay also be used, usually in conjunction with abrasive particles, andinclude calcium chelators, polymers, surfactants, enzymes and oxidisingagents.

EP 1 935 395 describes a novel optical approach to tooth whitening. Onbrushing with the toothpaste described in this publication, a bluepigment (in particular blue covarine) is deposited onto the toothsurface, where it is able to change the optical effects of the toothsurface, and enhance the measurement and perception of tooth whiteness.This toothpaste is intended to produce a temporary tooth whiteningeffect that can be reapplied as frequently as desired, as it contains noharsh chemicals, but is not intended to produce any permanent changes tothe colour of the teeth.

The present inventors have now found that certain pearlescent pigmentscan produce superior temporary tooth whitening effects when used in acontext similar to that described in EP 1 935 395.

US2005/0175552 and US2005/0287084 describe compositions for impartingwhiteness to teeth, which may include various types of pearlescentparticle. The compositions described are evaporative solvent-basedsystems intended for direct application to the teeth by adhesion orpainting, after which they dry to form a film.

SUMMARY OF THE INVENTION

The present invention provides an oral care composition suitable fordelivering a temporary whitening effect to the surface of teeth, thecomposition comprising:

a continuous phase comprising water or polyhydric alcohol or a mixturethereof;

a tooth surface whitening agent which is dispersed in the continuousphase, and

a deposition aid for the tooth surface whitening agent;

characterised in that the tooth surface whitening agent is a pearlescentpigment in an amount of at least 0.1% by weight based on the totalweight of the composition, the pearlescent pigment being formed bycoating one or more metal oxide layers onto particles of an inorganicsubstrate.

DETAILED DESCRIPTION OF THE INVENTION

Tooth Surface Whitening Agent

The composition of the invention comprises a tooth surface whiteningagent which is dispersed in the continuous phase of the composition.

The tooth surface whitening agent is a pearlescent pigment which isformed by coating one or more metal oxide layers onto particles of aninorganic substrate.

The term “pearlescent” in the context of the present invention denotes apigment in the form of particles which each reflect and partiallytransmit the incident light. The colour effects obtained are associatedwith the lamellar structure of these particles and are derived from thephysical laws of the optics of thin layers.

Suitable inorganic substrates used to form the pearlescent pigment arecomposed of particles with a thin platelet or flaky morphology. The term“thin platelet or flaky morphology” in the context of the presentinvention generally means that such particles will have an aspect ratio(lateral diameter to thickness) of at least 5, preferably at least 10,and a mean thickness in the range of 100 to 1000 nm, preferably in therange of 200 to 600 nm.

The inorganic substrates used to form the pearlescent pigment preferablyhave a fine particle size. The term “fine particle size” in the contextof the present invention generally means that the average particlediameter is less than 65 microns, and is most preferably less than 25microns. The term “diameter” as used herein, means the largest distanceacross the major axis of the particle. Diameter can be determined by anysuitable method known in the art, such as particle size analyzerMastersizer 2000 manufactured by Malvern Instruments.

Examples of suitable inorganic substrates include natural or syntheticmica flakes (such as muscovite, phlogopite, fluorophlogopite andbiotite), other sheet silicates (such as talc, kaolin and sericite),glass platelets, silica flakes, borosilicate flakes and alumina flakes.The substrate need not be totally transparent but should, preferably,have at least about 75% transmission. Natural or synthetic mica flakesare preferred.

The pearlescent pigment is formed by coating one or more metal oxidelayers onto the particles of inorganic substrate which are describedabove.

Examples of suitable metal oxides include TiO₂, Fe₂O₃, TiFe₂O₅, titaniumsuboxides, Fe₃O₄, Cr₂O₃, Al₂O₃, SiO₂, ZrO₂, ZnO, SnO₂, CoO, Co₃O₄, VO₂,V₂O₃, Sn(Sb)O₂ or mixtures thereof.

Preferred pearlescent pigments for use in the invention include naturalor synthetic mica flakes coated with TiO₂ and/or Fe₂O₃.

The colour of the pearlescent pigment is a function of the thickness ofthe metal oxide layer. The required thickness for a specific colour maybe different for different materials. Preferred pigment colours in thecontext of the present invention are silver, white, blue and mixturesthereof.

Particularly preferred pearlescent pigments for use in the invention arenatural or synthetic mica flakes coated with TiO₂, the pigment having asilver-white colour. For TiO₂, a layer of 40 nm to 60 nm or a wholenumber multiple thereof gives a silver-white colour.

The most preferred pearlescent pigments for use in the invention arenatural or synthetic mica flakes coated with TiO₂, the pigment having asilver-white colour and the pigment having a mean particle diameter (asdefined above) which is less than 25 microns, most preferably less than15 microns. Such materials are commercially available, for example underthe tradenames Timiron® and Candurin®, e.g. Timiron® Supersilk MP-1005(ex Merck) and Candurin® Silver Fine (ex Merck).

Other examples of suitable pearlescent pigments for use in the inventionare natural or synthetic mica flakes coated with TiO₂ and having a blueor silver-blue colour. For TiO₂, a layer of 100 nm to 130 nm or a wholenumber multiple thereof gives a blue colour. Other absorption colourantscan also be precipitated on top of or simultaneously with the TiO₂layer. Examples are blue pigments such as ferric ferrocyanide, cobaltblue and copper phthalocyanine. Such materials are commerciallyavailable for example under the tradenames Mearlin®, Colorona® andDynacolour®, e.g. Mearlin® Sparkle Blue (ex BASF), Colorona® Dark Blue(ex Merck) and Dynacolour® BB9639ZB15C (ex BASF).

Mixtures of any of the above described materials may also be used.

The amount of pearlescent pigment (as defined above) in compositions ofthe invention is at least 0.1% by weight based on the total weight ofthe composition. The amount of pearlescent pigment suitably ranges from0.1 to 5.0%, preferably from 0.1 to 3.0%, more preferably from 0.2 to2.0% by total weight pearlescent pigment (as defined above) based on thetotal weight of the composition.

Deposition Aid

The composition of the invention comprises a deposition aid for thetooth surface whitening agent.

The term “deposition aid” in the context of this invention generallymeans a material which aids deposition of the tooth whitening agent fromthe continuous phase of the composition onto the surface of teeth duringuse of the composition. Use of the composition in the context of thisinvention typically involves application of the composition to the oralcavity, followed by brushing and/or rinsing).

Suitable deposition aids work by having affinity for both thepearlescent pigment (as defined above) and the surface of the teeth.

Preferred deposition aids are able to aid the deposition of thepearlescent pigment onto the teeth such that tooth surface whiteness isenhanced by at least 20% and more preferably by at least 100%, incomparison to the value obtained for teeth treated in an equivalentmanner with a control formulation using the same amount of pearlescentpigment in the absence of the deposition aid.

A convenient measure of enhanced tooth surface whiteness is delta b*measured using a chromameter. A negative value of delta b* indicates ayellow to blue colour shift which has been shown to be one of theprimary drivers of tooth surface whiteness as perceived by the consumer.

Accordingly, preferred deposition aids are able to aid the deposition ofthe pearlescent pigment onto the teeth such that the negative value ofdelta b* is augmented by at least 20% and more preferably by at least100%, in comparison to the value obtained for teeth treated in anequivalent manner with a control formulation using the same amount ofpearlescent pigment in the absence of the deposition aid.

A simple empirical model for establishing the effect of the depositionaid is as follows:

Polished hydroxyapatite discs are first placed in sterile human salivafor 2 hours to allow a pellicle to form. The discs are then rinsed inwater and baseline colour measurements made (using, for example, aMinolta chromameter CR300). The discs are then brushed with either (a) asuspension of the pearlescent pigment in water; or (b) a suspension ofthe pearlescent pigment in water at the same concentration as in (a),together with the deposition aid. The brushing is best performed using abrushing machine. Following rinsing, the colour of the discs is thenre-measured and the change in delta b* is recorded for both treatment(a) and treatment (b). From a comparison of these data, the effect ofthe deposition aid is readily seen.

Suitable deposition aids for use in the invention include polymericmaterials.

Polymeric materials for use as deposition aids in the invention may benaturally or synthetically-derived, and may be ionic or nonionic innature.

Preferably such polymeric materials are high molecular weight. The term“high molecular weight” in this particular context generally means thatthe polymeric material has a molecular weight of at least 20,000, morepreferably at least 50,000 g/mol, most preferably at least 90,000 g/mol.A suitable method to determine the molecular weight of such polymericmaterials is gel permeation chromatography against a polyethylene glycolstandard.

A preferred class of polymeric material for use as deposition aids inthe invention includes high molecular weight polysaccharides havinganionic side groups along the polymer main chain.

Specific examples of such materials include gellan gum and carrageenan.The molecular structure of gellan gum is a straight chain based onrepeating glucose, rhamnose and glucuronic acid units. Carrageenan is acell wall hydrocolloid found in certain species of seaweeds belonging tored algae and is composed of repeating units of galactose and3,6-anhydrogalactose with sulfate esters in varying amount and locationdepending on the type of carrageenan.

A particularly preferred class of polymeric material for use asdeposition aids in the invention includes high molecular weightpolyuronates. Polyuronates are typically linear polymers of uronic acidresidues. The term “uronic acid residues” as used herein includes uronicacid groups in the form of the free acid or in the form of a derivativethereof, such as a salt, ester or anhydride.

Suitable polyuronates for use as deposition aids in the invention areformed from (1→4)-linked uronic acid residues selected fromα-D-galacturonate, α-L-guluronate, β-D-mannuronate, β-D-glucuronate andmixtures thereof.

Preferred polyuronates for use as deposition aids in the invention arepectin and alginates.

Pectin is naturally present in the cell walls of plants and functions asa binding agent. A common source for extracting pectin is citrus peel.Naturally occurring pectin is an integral part of the complex structurewhich imparts stability to a plant. In this case, the pectin comprisingseveral different types of neutral sugar molecules, which are present ina complex, defined pattern which contains sequences of (1→4)-linkedα-D-galacturonate residues which are sandwiched with sequences ofneutral sugar molecules such as rhamnose, galactose, arabinose and othersugar types which describe a well-branched structure. When pectin isextracted, a large part of the branched structure usually disappears anda relatively straight chain, the majority of which consists of(1→4)-linked α-D-galacturonate residues, remains. Extracted pectinusually contains more than 65% α-D-galacturonate residues. Theα-D-galacturonate residues may generally be in the form of the freeacid, or the salt of the free acid, or the methyl ester of the freeacid. When more than 50% of the α-D-galacturonate residues are in methylester form, the pectin is then classified as being high-methyl esterpectin, and when less than 50% of the α-D-galacturonate residues are inmethyl ester form it is consequently classified as being low-methylester pectin. Some pectins are treated during manufacture with ammoniato produce amidated pectins, in which some of the α-D-galacturonateresidues are converted to carboxylic acid amide groups.

Preferred examples of suitable pectins for use in the invention arelow-methyl ester pectins. Such materials may be amidated (commerciallyavailable under the tradename GENU® Pectin X-916-02, ex CP Kelco) or,more preferably, non-amidated (commercially available under thetradename GENU® Pectin LM-18, ex CP Kelco).

Alginates are a particularly preferred class of polyuronate for use asdeposition aids in the invention. “Alginate” is the general name foralginic acid and its salts. Alginates are polysaccharides which may beisolated from brown algae such as Laminaria hyperborea and lessoniafound in coastal waters, and may be characterised as linear copolymerswhich contain sequences of (1→4)-linked β-D-mannuronate (M) andα-L-guluronate (G) residues, respectively. Naturally occurring alginatehas a block-like structure in which stretches of poly-α-L-guluronate areinterspersed by stretches of poly-β-D-mannuronate, and byheteropolymeric regions in which both residues occur in arrangementswhich can range from almost statistically random to almost regularlyalternating. The number ratio of mannuronate to guluronate residues isknown as the M:G ratio and can vary according to the nature or growthconditions of the source material.

Sodium alginate is the most preferred alginate for use as a depositionaid in the invention. The sodium alginate may for example be of the“high mannuronic” type, characterised by an M:G ratio of at least 1:1,generally at least 1.5:1. Such materials are commercially available, forexample under the tradename MANUCOL® DH (ex FMC BioPolymer).Alternatively, and in some cases preferably, the sodium alginate may beof the “high guluronic” type, characterised by an M:G ratio of from0.1:1 to less than 1:1, generally from 0.2:1 to 0.8:1. Such materialsare commercially available, for example under the tradename MANUGEL® GMB(ex FMC BioPolymer).

Mixtures of any of the above described materials may also be used.

The amount of deposition aid (as defined above) in compositions of theinvention suitably ranges from 0.01 to 5.0%, preferably from 0.1 to3.0%, more preferably from 0.2 to 2.0% by total weight deposition aid(as defined above) based on the total weight of the composition.

Product Form

The composition of the invention comprises a continuous phase comprisingwater or polyhydric alcohol or a mixture thereof.

Examples of suitable product forms for compositions of the inventioninclude dentifrices, mouthwashes, chewing gums and lozenges.

Preferred product forms for compositions of the invention are thosewhich are suitable for brushing and/or rinsing the surfaces of the oralcavity.

In such preferred product forms, the amount of water and/or polyhydricalcohol will generally be at least 10%, preferably at least 30%, morepreferably at least 50% by total weight water and/or polyhydric alcoholbased on the total weight of the composition.

An example of a preferred type of product form in the context of thepresent invention is a dentifrice. The term “dentifrice” generallydenotes formulations which are used to clean the surfaces of the oralcavity. The dentifrice is an oral composition that is not intentionallyswallowed for purposes of systemic administration of therapeutic agents,but is applied to the oral cavity, used to treat the oral cavity andthen expectorated. Typically the dentifrice is used in conjunction witha cleaning implement such as a toothbrush, usually by applying it to thebristles of the toothbrush and then brushing the accessible surfaces ofthe oral cavity. Preferably the dentifrice is in the form of a paste ora gel (or a combination thereof).

A dentifrice composition according to the invention will usually containa liquid continuous phase in an amount of from 40 to 99% by weight basedon the total weight of the dentifrice. Such a liquid continuous phasewill typically comprise a mixture of water and polyhydric alcohol invarious relative amounts, with the amount of water generally rangingfrom 10 to 45% by weight (based on the total weight of the dentifrice)and the amount of polyhydric alcohol generally ranging from 30 to 70% byweight (based on the total weight of the dentifrice). Typical polyhydricalcohols include humectants such as glycerol, sorbitol, polyethyleneglycol, polypropylene glycol, propylene glycol, xylitol (and otheredible polyhydric alcohols), hydrogenated partially hydrolyzedpolysaccharides and mixtures thereof.

A dentifrice composition according to the invention will generallycontain further ingredients to enhance performance and/or consumeracceptability such as abrasive cleaning agent, binder or thickeningagent, and surfactant.

For example, a dentifrice will usually comprise an abrasive cleaningagent in an amount of from 3 to 75% by weight based on the total weightof the dentifrice. Suitable abrasive cleaning agents include silicaxerogels, hydrogels and aerogels and precipitated particulate silicas;calcium carbonate, dicalcium phosphate, tricalcium phosphate, calcinedalumina, sodium and potassium metaphosphate, sodium and potassiumpyrophosphates, sodium trimetaphosphate, sodium hexametaphosphate,particulate hydroxyapatite and mixtures thereof.

Furthermore, the dentifrice will usually contain a binder or thickeningagent in an amount of from 0.5 to 10% by weight based on the totalweight of the dentifrice. Suitable binders or thickening agents includecarboxyvinyl polymers (such as polyacrylic acids cross-linked withpolyallyl sucrose or polyallyl pentaerythritol), hydroxyethyl cellulose,hydroxypropyl cellulose, water soluble salts of cellulose ethers (suchas sodium carboxymethyl cellulose and sodium carboxymethyl hydroxyethylcellulose), natural gums (such as carrageenan, gum karaya, guar gum,xanthan gum, gum arabic, and gum tragacanth), finely divided silicas,hectorites, colloidal magnesium aluminium silicates and mixturesthereof.

Furthermore, the dentifrice will usually contain a surfactant in anamount of from 0.2 to 5% by weight based on the total weight of thedentifrice. Suitable surfactants include anionic surfactants, such asthe sodium, magnesium, ammonium or ethanolamine salts of C₈ to C₁₈ alkylsulphates (for example sodium lauryl sulphate), C₈ to C₁₈ alkylsulphosuccinates (for example dioctyl sodium sulphosuccinate), C₈ to C₁₈alkyl sulphoacetates (such as sodium lauryl sulphoacetate), C₈ to C₁₈alkyl sarcosinates (such as sodium lauryl sarcosinate), C₈ to C₁₈ alkylphosphates (which can optionally comprise up to 10 ethylene oxide and/orpropylene oxide units) and sulphated monoglycerides. Other suitablesurfactants include nonionic surfactants, such as optionallypolyethoxylated fatty acid sorbitan esters, ethoxylated fatty acids,esters of polyethylene glycol, ethoxylates of fatty acid monoglyceridesand diglycerides, and ethylene oxide/propylene oxide block polymers.Other suitable surfactants include amphoteric surfactants, such asbetaines or sulphobetaines. Mixtures of any of the above describedmaterials may also be used.

Another example of a preferred type of product form in the context ofthe present invention is a mouthwash. The term “mouthwash” generallydenotes liquid formulations which are used to rinse the surfaces of theoral cavity and provide the user with a sensation of oral cleanlinessand refreshment. The mouthwash is an oral composition that is notintentionally swallowed for purposes of systemic administration oftherapeutic agents, but is applied to the oral cavity, used to treat theoral cavity and then expectorated.

A mouthwash composition according to the invention will usually containan aqueous continuous phase. The amount of water generally ranges from70 to 99% by weight based on the total weight of the mouthwash.

A mouthwash composition according to the invention will generallycontain further ingredients to enhance performance and/or consumeracceptability, such as the humectants and surfactants mentioned abovefor dentifrices. The amount of humectant generally ranges from 5 to 20%by weight based on the total weight of the mouthwash and the amount ofsurfactant generally ranges from 0.1 to 5% by weight based on the totalweight of the mouthwash.

Compositions of the present invention (such as in particular dentifricesor mouthwashes) may also contain further optional ingredients customaryin the art such as fluoride ion sources, anticalculus agents, buffers,flavouring agents, sweetening agents, colouring agents, opacifyingagents, preservatives, antisensitivity agents and antimicrobial agents.

The invention is further illustrated with reference to the following,non-limiting Examples.

EXAMPLES Experimental Method

Extracted human anterior teeth were cleaned and the roots mounted inperspex blocks. Any remaining exposed dentine was coated in nailvarnish. The teeth were allowed to fully hydrate in deionised water forseveral days before immersion in whole human saliva for 2 hours to forma pellicle.

The baseline colour of the teeth was measured with a colorimeter in theCIELAB mode. The teeth were then randomly allocated to their respectivetreatment groups (n=8) which typically consisted of an aqueous mixtureof 1% w/w pearlescent pigment (as defined above) plus 1% w/w depositionaid (as defined above).

Controls included a system which is representative of the preferredpigment & deposition aid combination according to EP 1 935 395 (i.e.0.025% w/w Blue Covarine pigment plus 0.1% w/w GANTREZ®S97 depositionaid ex ISP); and a system without deposition aid (i.e. pearlescentpigment alone).

The treatment time was 1 minute, followed by extensive water rinse.

The colour of the teeth was again measured and changes in CIELABcalculated as Delta L*, Delta a* and Delta b*. For “blue” colouredmicas, reduction in b* (i.e. tooth yellowness) was the main parameterfor efficacy. For “white” or “silver-white” coloured micas, increase inL* (brightness) was also considered.

Experiment 1 Blue Micas Plus Deposition Polymer

Example Treatment Delta b* (s.d.) Comparative Colorona ® Dark Blue Mica−1.23 (0.44) Example A Example 1 Colorona ® Dark Blue Mica + −12.51(2.46)  MANUCOL ® DH Example 2 Dynacolour ® Blue Mica + −10.87 (2.12) MANUCOL ® DH Example 3 Mearlin ® Sparkle Blue + −3.26 (1.21) MANUCOL ®DH Comparative Blue Covarine + GANTREZ ® S97 −1.62 (0.54) Example B

This series of results shows that Examples 1 to 3 according to theinvention provide superior reduction in tooth yellowness when comparedto a system without deposition aid (Comparative Example A) or whencompared to a system which is representative of the preferred pigment &deposition aid combination according to EP 1 935 395 (ComparativeExample B).

Experiment 2 White/Silver-White Micas Plus Deposition Polymer

Example Treatment Delta L* (s.d.) Delta b* (s.d.) Comparative Timiron ®Supersilk 0.17 (0.98) −0.33 (0.36) Example C MP-1005 Example 4 Timiron ®Supersilk 4.12 (1.69) −3.01 (1.56) MP-1005 + 0.5% MANUCOL ® DH Example 5Timiron ® Supersilk 7.51 (2.28) −4.36 (1.80) MP-1005 + 1.0% MANUCOL ® DHExample 6 Timiron ® Supersilk 2.15 (0.94) −1.49 (0.61) MP-1005 + 1.0%GENU ® Pectin X- 916-02 Example 7 Candurin ® Silver 5.93 (2.10) −3.05(1.31) Fine + 1.0% MANUCOL ® DH Example 8 Timiron ® Pearl 4.19 (1.68)−3.04 (0.67) Sheen + 1.0% MANUCOL ® DH Comparative Blue Covarine + −1.13(0.40)  −1.62 (0.54) Example B GANTREZ ® S97

This series of results shows that Examples 4 to 8 according to theinvention provide superior reduction in tooth yellowness and increase intooth brightness, when compared to a system without deposition aid(Comparative Example C) or when compared to a system which isrepresentative of the preferred pigment & deposition aid combinationaccording to EP 1 935 395 (Comparative Example B).

Experiment 3 Comparison of Deposition Polymers

Example Treatment Delta L* (s.d.) Delta b* (s.d.) Example 7 Candurin ®Silver 5.93 (2.10) −3.05 (1.31) Fine + 1% MANUCOL ® DH Example 9Candurin ® Silver 0.91 (0.67) −0.85 (0.51) Fine + 1% GANTREZ ® S97Example 10 Candurin ® Silver 0.92 (0.43) −0.50 (0.25) Fine + 2% PEG 32

This series of results shows that MANUCOL® DH is an especially effectivedeposition aid for pearlescent pigments such as Candurin® Silver Fine.

Experiment 4 Mouthwash Formulations

Mouthwash formulations were prepared having ingredients as shown in thefollowing Table:

Example Example Example Example Comp. Ex. 11 12 13 14 D Ingredient (wt%) Water 82.26 82.26 82.26 82.26 82.26 Sorbitol (70%) 12.0 12.0 12.012.0 12.0 PEG40 hydrogenated castor 2.5 2.5 2.5 2.5 2.5 oil Sodiumlauryl sulphate 0.34 0.34 0.34 0.34 0.34 Phenoxyethanol 0.3 0.3 0.3 0.30.3 Benzyl alcohol 0.3 0.3 0.3 0.3 0.3 Flavour 0.3 0.3 0.3 0.3 0.3Mica⁽¹⁾ 1.0 1.0 1.0 1.0 1.0 MANUCOL ® DH⁽²⁾ 1.0 — — — — MANUGEL ® GMB⁽³⁾— 1.0 — — — GENU ® Pectin X-916-02⁽⁴⁾ — — 1.0 — — GENU ® Pectin LM-18⁽⁵⁾1.0 — ⁽¹⁾TIMIRON ® Supersilk MP-1005 (ex Merck), white mica with aparticle size of c. 6 microns. ⁽²⁾Sodium alginate, high mannuronic acidcontent, ex FMC Biopolymer ⁽³⁾Sodium alginate, high guluronic acidcontent, ex FMC Biopolymer ⁽³⁾Amidated low methoxy pectin, ex CP Kelco⁽⁴⁾Non-amidated low methoxy pectin, ex CP Kelco

The mouthwash samples were tested on extracted molar teeth mounted inplastic. Prior to use, the teeth were immersed in gamma-irradiated humansaliva for 24 hours to generate a pellicle layer. Each mouthwash wastested on 6 randomly selected teeth.

The colour of each tooth was measured using a Minolta CR321 Chroma Meter(45° illumination, 0° viewing angle, 3 mm diameter measuring area). Sixreadings were taken from the front face of the tooth to provide anaverage colour. Two teeth were then immersed in the mouthwash solutionwhich was being continuously stirred on a magnetic stirrer. After 60seconds the teeth were removed, excess solution removed by shaking andthe colour remeasured. The teeth were then gently agitated in 24° FHwater for 10 seconds and measured again.

Results

Delta Delta L* (s.d.) b* (s.d.) Delta Delta post- post- L* (s.d.) b*(s.d.) Example treatment treatment post-rinse post-rinse Comp. Ex. D1.389 −0.940 0.342 −0.437 (0.395) (0.283) (0.076) (0.510) Example 112.668 −2.042 −0.098 −0.300 (1.015) (1.085) (0.380) (0.289) Example 124.159 −2.932 0.768 −0.566 (0.447) (1.008) (0.426) (0.662) Example 132.474 −1.681 0.264 −0.404 (1.073) (0.459) (0.264) (0.270) Example 145.142 −3.028 4.144 −2.996 (1.584) (1.347) (1.786) (1.207) The whitenessbenefit is obtained in two ways, by increasing the lightness (L*) valueand/or by decreasing the b* (which counters the natural yellowness ofthe teeth).

This series of results shows that post-treatment, Examples 11 to 14according to the invention provide superior increase in L*, whencompared to a system without deposition aid (Comparative Example D).Examples 11, 12 and 14 provide significant increases in L*. Examples 12and 14 also provide significant decreases in b*, relative to theComparative Example. Example 14 also provides improved resultspost-rinsing, implying greater post-rinse retention of this system onthe teeth.

The invention claimed is:
 1. An oral care composition comprising: acontinuous phase comprising at least one of water, polyhydric alcohol ora mixture thereof; a tooth surface whitening agent which is dispersed inthe continuous phase, and a deposition aid for the tooth surfacewhitening agent; wherein the tooth surface whitening agent comprises apearlescent pigment in an amount of from 1 to 5% by weight based on thetotal weight of the oral care composition, wherein the pearlescentpigment comprises particles of at least one inorganic substrate, whereinthe particles have: i) a coating of one or more metal oxide layers, andii) at least one of: 1) an average particle diameter of less than 65microns and 2) a mean particle diameter of less than 25 microns; andwherein the deposition aid comprises a polyuronate having a molecularweight of at least 20,000 g/mol.
 2. The oral care composition accordingto claim 1, in which the the particles of the pearlescent pigment areselected from at least one of natural and synthetic mica flakes coatedwith at least one of TiO₂ and Fe₂O₃.
 3. The oral care compositionaccording to claim 2, in which the particles have the average or themean particle diameter of less than 15 microns.
 4. The oral carecomposition according to claim 1, in which the deposition aid is sodiumalginate.
 5. The oral care composition according to claim 1, which is inthe form of a dentifrice or a mouthwash.
 6. The oral care compositionaccording to claim 1, in which the particles have the average or themean particle diameter of less than 15 microns.
 7. The oral carecomposition according to claim 1, wherein the polyuronate is at leastone of pectin and alginate.
 8. The oral care composition according toclaim 1, wherein the polyuronate comprises (1→4)-linked uronic acidresidues selected from the group consisting of: α-D-galacturonate,α-L-guluronate, β-D-mannuronate, β-D-glucuronate and mixtures thereof.9. The oral care composition according to claim 1, wherein a ratio ofthe amount of pearlescent pigment to an amount of the deposition aid inthe oral care composition is 2:1 to 1:1.